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LBoyett Petroleum May 18, 2000 419 South Main Street, Manteca, California Page 3 Work Plan for Lateral Extent Lof Groundivater Contamination (Addendum) present in the soil samples collected from the monitoring wells until the point of the soil/water interface (capillary fringe). WHF proposes five (5) shallow soil borings, four (4) will be to a depth of approximately twenty-five feet (25'), thereby not violating the clay layer that is present between twenty-six feet (26') and twenty-nine feet (29'). These four (4) borings will be converted r monitoring wells to confirm the presence or absence petroleum car ons in the �•, groundwater underlying the site. A single soil boring not o be converted to a monitoring well) will be completed to a depth of approximately fift eet (50') to determine the vertical extent of soil and groundwater contamination. The number of borings/monitoring wells, +o /� Uj and the depths of the wells, may be increased based on the field observations and the judgement of the on-site professional from VaIF, Inc. at the time of drilling. LThe locations of these monitoring wells are shown in Figure 3 and are described below: L • One MW placed north of MWA • One MW placed west of MW-1 along the western fence line. • One MW placed to the south of MW-1 along the western wall of the Mini Mart L • One MW placed to the southeast of MW-2 The data collected during this scope of work will be used to define the migration of the L groundwater plume, to complete a feasibility study, and to make recommendations regarding future work at this site. The feasibility study will evaluate the following remediation options: • Natural biological attenuation • Enhanced biological attenuation using Oxygen Release Compound • Groundwater pump and treat L 3.1 Drilling LPermits will be obtained, as necessary, for the borings and monitoring well before drilling begins. The single soil boring (not to be completed as a monitoring well) will be completed using the cone penetrometry test method to obtain relevant lithological and hydrological data. The remaining four (4) soil borings/monitoring wells will be accomplished using a mobile mounted drilling rig employing the use of a hollow stem flight auger no less than 3 1/4-inch i.d. and 8-inch o.d. All drilling equipment will be thoroughly cleaned before drilling begins, to prevent the introduction of contamination from off site, and between borings to prevent cross contamination. L